In the conventional method for determining position and/or velocity of a target object by comparing the transmitted wave emitted from a wave transmitter and the reflected wave reflected back by the target object, the distance between the wave transmitter and the target object is determined by measuring the time interval between the emission of a pulse of the transmitted wave and the reception of a pulse of the reflected wave, while the velocity of the target object is determined from the difference in the frequency between the transmitted wave and the received wave resulting from the Doppler effect. In the above-described conventional methods, the information on the position and/or velocity of the target object is obtained by analyzing the wave form characteristics of the received signal in the time domain or frequency domain in comparison with the wave form of the transmitted wave. The present invention teaches methods for determining the velocity of a target object by measuring the phase angle difference between the transmitted wave and the received wave and determining the velocity of the target object as a function of the time rate of change of the phase angle difference, which methods teach how to measure the velocity of a target object by using an ordinary radar without employing the principles of the Doppler radar.